Electrostatic adhesion of dry powders to macro fertilizers

ABSTRACT

A method for electrostatically adhering an agricultural input powder to an agronomic carrier is described. A dry nutrient powder is electrostatically charged in a charging chamber which has a grounded metal component such that the electrostatically charged powder moves towards the metal component. The agronomic carrier is then passed by the charged powder such that the charged powder adheres to the carrier.

FIELD OF THE INVENTION

The present invention relates generally to the field of agriculturalinputs. More specifically, the present invention relates to a method ofcoating an agronomic carrier with an agricultural input powder.

BACKGROUND OF THE INVENTION

Studies of powdered fertilizers or nutrients have shown them to beeffective fertilizers, being essentially equivalent to granularapplications. However, the practical considerations of applying powderedproducts on a field scale meant that these products have not beenavailable to farmers and producers. For example, most oxide productscome in high analysis (60-80 percent actual metal) while mostmicronutrients are applied in low units per land measure (e.g. 1-10pounds actual per acre). Furthermore, many micronutrient products areapplied in heterogeneous blends with other fertilizers (nitrogenphosphate etc.) These products and/or blends typically have densities inthe 45-65 lb per cubic foot range. Existing micronutrient products aretypically in the 95+ density range meaning that the blend does not holdits integrity during extended storage as is common in agriculture or ifthe product is transported over rough terrain. In addition, the higherdensity means that the nutrients are not spread evenly on the field.

Past work with powdered nutrients by the inventors has shown that it ispossible to coat macro fertilizer with 0.1 to 2 percent weight to weightof powdered nutrients directly onto dry macro fertilizers such as urea,phosphate granules, potash granules and the like, without the use ofbinders, as discussed in U.S. Pat. No. 7,445,657. However, in some casesit can be difficult to obtain a coating above 1 percent (w/w) on certaincarriers, for example, if the prills or granules have a substantiallysmooth surface or are larger than average. Furthermore, as discussedbelow, using this method, it is often only possible to coat the outersurface of the carrier with a single layer of the powder.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodfor adhering a nutrient powder to an agronomic carrier comprising:

electrostatically charging a quantity of dry powder of an agriculturalinput in a charging chamber comprising a grounded metal component suchthat the electrostatically charged powder coats the agronomic carrierwhich then moves towards the grounded metal component; and

As will be apparent to one of skill in the art, an agricultural inputrefers generally to different types of factors which relate toagricultural productivity. These can include materials: that provideplant nutrition, for example, fertilizers; that provide crop protection,for example, pesticides and herbicides; that add specific biologicalactivities to the soil, for example, inoculants; or materials thatprovide soil amending properties, for example, changing pH.

Examples of suitable agronomic carriers include but are by no meanslimited to granules, prills, seeds, fertilizer pellets, fertilizerprills, fertilizer granules, liming materials, gypsum, pelleted manures,inert carriers such as zeolite, organic grits or organic pellets.

Preferably, the electrostatic charge is applied to the powder at ratesranging from 15 kV to 100 kV. In other embodiments, the electrostaticcharge may be applied at a rate ranging from between 25 kV to 100 kV,from 15 kV to 25 kV, from 15 kV to 50 kV, from 15 kV to 75 kV, from 25kV to 75 kV, from 25 to 50 kV, from 50 to 75 kV, from 50 kV to 100 kV orfrom 75 kV to 100 kV.

Preferably, the electrostatic charging is carried out at an air pressurebetween 8 to 20 psi or 0-4 BAR.

Preferably, the particle size of the powders is of a size wherein atleast 80 percent are between 10 and 90 microns.

According to another aspect of the invention, there is provided afertilizer product comprising a dry agronomic carrier coated with a finedry powder of at least one agricultural input, wherein the agriculturalinput powder has been ground such that at least half of the particlesare of an average diameter between 10 and 90 microns, said powder beingpresent on the carrier at 0.1%-5.0% (w/w) of the carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the method of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described. All publications mentioned hereunderare incorporated herein by reference.

DEFINITIONS

As used herein, “nutrient” refers to micronutrients, secondary nutrientsand macronutrients, as well as soil amendments, for example, zinc,copper, manganese, boron, calcium, iron, calcium sulfate (gypsum),magnesium, molybdenum, chloride, selenium, phosphate, nitrogen,potassium and sulfur.

As used herein, “micronutrients” refers to elements required in small ortrace amounts for plant growth, for example, molybdenum, nickel, copper,zinc, manganese, boron, iron and chloride.

As used herein, “macronutrients” refers to elements typically requiredin large amounts for plant growth, for example, phosphorus, magnesium,calcium, potassium, nitrogen, oxygen, carbon and hydrogen.

As used herein, “higher analysis” refers to guaranteed minimum analysis.That is, higher analysis means higher concentration of activeingredients versus carriers or impurities.

As used herein, “density” refers to kilograms per cubic meter.

As used herein, “agronomic carrier” refers to an agricultural product,for example, but by no means limited to: seeds; nitrogen, phosphate,potassium, sulfur, calcium and/or magnesium fertilizer products; ureaprills; dry or granular fertilizer products; and inert or biodegradablepellets.

As used herein, “electrostatic charge” refers to an electrical dischargeor contact electrification in which ions are generated and/ortransferred.

The electrostatic charge can be applied by any suitable means known inthe art. One example is triboelectric charging, which is a type ofcontact electrification in which certain materials become electricallycharged after they come into contact with another different material.Another example is corona discharge wherein ions are generated andpassed to nearby areas of lower potential.

As discussed herein, the inventors have conducted tests in order toaddress the difficulties discussed above. Specifically, the inventorshave determined that the maximum coating capacity can be increased bysubjecting the powder to a fertilizer handling system which comprisesapplying an electrostatic charge to the powder.

According to an aspect of the invention, there is provided a method foradhering an agricultural input powder to an agronomic carriercomprising:

electrostatically charging a quantity of dry agricultural input powderin a charging chamber comprising a grounded metal component and bringingthe agronomic carriers in contact with the ground such that the carrierbecomes grounded such that the electrostatically charged powder movestowards the grounded agronomic carrier; and passing the agronomiccarriers by the charged powder such that the charged powder adheres tothe carrier.

It is of note that “passing” refers to the agronomic carriers beingmoved past the reservoir of charged agricultural input powder insufficient proximity to the powder that the powder will adhere to thecarrier, as discussed below.

As will be appreciated by one of skill in the art, the invention canalso be considered a method for coating an agronomic carrier with anagricultural input powder.

Preferably, the electrostatic charge is applied to the powder at ratesranging from 15 kV to 100 kV. In other embodiments, the electrostaticcharge may be applied at a rate ranging from between 25 kV to 100 kV,from 15 kV to 25 kV, from 15 kV to 50 kV, from 15 kV to 75 kV, from 25kV to 75 kV, from 25 to 50 kV, from 50 to 75 kV, from 50 kV to 100 kV orfrom 75 kV to 100 kV.

Preferably, the electrostatic charging was carried out an air pressurebetween 0 TO 4 BAR.

As will be apparent to one of skill in the art, an “agricultural input”refers generally to different types of factors which relate toagricultural productivity, in the context of the instant invention,these can include for example but by no means limited to materials thatprovide plant nutrition, for example, fertilizers; that provide cropprotection, for example, pesticides and herbicides; that add specificbiological activities to the soil, for example, inoculants; or materialsthat provide soil amending properties. As is known to one of skill inthe art, a soil amendment is any material added to a soil to improve itsphysical properties, such as water retention, permeability, waterinfiltration, drainage, aeration and structure. The goal of soilamendment is to provide a better environment for roots.

Examples of suitable agronomic carriers include but are by no meanslimited to granules, prills, seeds, fertilizer pellets, fertilizerprillls, fertilizer granules, liming materials, gypsum, pelletedmanures, inert carriers such as zeolite, organic grits or organicpellets. The agricultural input powder may be, for example, a powderedfungicide, an insecticide, a nutrient such as nitrogen, phosphorus,potassium, calcium, magnesium; a fertilizer powder or component thereof;an inoculant, a soil amendment, or a micronutrients such as zinc,copper, manganese, boron, iron, magnesium, molybdenum, chloride,selenium, phosphate, nitrogen, potassium, sulfur or combinationsthereof. By way of illustrative but in no way limiting examples, coppermay be copper (cupric): hydroxide, chloride, sulfate, oxide, oxysulfate,nitrate, carbonate, ammonium carbonate, cupric chloride dihydrate,proteinate, acetate, citrate, chelate, complex, or sequestered; zinc maybe zinc: acetate, amoniated zinc, ammonium chloride, sulfate, oxide,oxysulfate, nitrate, chloride, citrate, chelate, or complex sequestered;manganese (manganous) may be manganese: nitrate, chloride, sulfate,oxide, oxysulfate, acetate anhydrous, carbonate, potassium manganesesulfate, acetate tetrahydrate, nitrate hexahydrate, citrate, chelate, orcomplex sequestered. Boron may be: boric acid, sodium borate, potassiumtetraborate tetrhydrate, calcium borate, calcium-sodium borate,(disodium octoborate tetrahydrate), (orthoboric acid), or Calcium may becalcium: carbonate, chloride, sulfate, gypsum, calcium borate, lime,nitrate, phosphate, citrate, chelate, or complex sequestered; and Ironmay be iron: sulfate, sulfate anhydrous, chloride, tetrahydrate,hexahydrate, nitrate, nitrate nonahydrate, chloride hexahydrate,ammonium citrate, ammonium sulfate, chelate, sequestered, proteinate orcomplex.

In some embodiments, the powder may be comprised of at least onenutrient in an oxide form, in a sulfate form or a combination of oxideand sulfate forms, as discussed below

The oxide form of the nutrient or nutrient powder may be, for example,copper oxide, produced, for example, by pyrolysis of copper nitrate,zinc oxide, produced, for example, by pyrolysis of zinc nitrate orcarbonate, manganese oxide or the like or boric acid, manganese sulfateor the like. As will be appreciated by one knowledgeable in the art,other nutrients or nutrient powders may be similarly prepared usingmeans known in the art.

As will be apparent to one knowledgeable in the art, the nutrient ornutrient powder may have any suitable or desirable nutrientconcentration, whether a single nutrient or a combination thereof. Thatis, the concentration of the nutrient(s) may vary from 1-99%, dependingupon intended use and application conditions. In some embodiments, thefertilizer may have a nutrient concentration of, for example: 5-45%zinc; 5-45% copper; 5-45% manganese or a mixture of 7% copper, 7% zincand 6% magnesium. As will be apparent to one knowledgeable in the art,the concentrations of the nutrients may be varied according to customerpreference, soil conditions and/or need, depending on the circumstances.

As will be apparent to one of skill in the art, the individual nutrientsmay be at any suitable level, for example, from trace amounts or 0.1% to50% actual.

The agricultural input powder is a dry, fine powder, typically ground orotherwise prepared or manipulated such that at least half of theparticles are of an average diameter between 10 and 90 microns in size.

As discussed herein, the inventors have been found that the instantmethod can be used to apply a powder coating to an agronomic carrier ofbetween 0.1% (w/w) to 5% (w/w) or of between 0.1% (w/w) to 4% (w/w) ofthe weight of the agricultural carrier. In other embodiments, thecoating is between 1.0% (w/w) to 5% (w/w) or 1.0% (w/w) to 4% (w/w). Inyet other embodiments, the agricultural input powder is between 1.5%(w/w) to 5% (w/w) or between 1.5% (w/w) to 4.0% (w/w). In yet otherembodiments, the agricultural input powder is between 2.0% (w/w) to 5%(w/w) or between 2.0% (w/w) to 4.0% (w/w). In still other embodiments,the agricultural input powder is between 2.5% (w/w) to 5% (w/w) orbetween 2.5% (w/w) to 4.0% (w/w). As discussed in U.S. Pat. No.7,445,657, the inventors previously hypothesized that static electricitygenerated during the mixing process promoted adhesion of the powder tothe carrier but that this was not an essential feature of the invention.

As will be appreciated by one of skill in the art, static electriccharges are very difficult to measure accurately. In addition, staticelectric charges can be difficult to reproduce consistently as severalfactors influence the generation of static electricity.

Furthermore, while the process disclosed in U.S. Pat. No. 7,445,657 isvery effective at coating an agronomic carrier, under certain conditionsand/or certain combinations of nutrient powders and agronomic carriers,the nutrient powder may not be spread evenly on the carrier or be spreadat the desired density. Furthermore, the process can also generate amoderate amount of dust during the application process which results insome loss of powder and also requires workers to take precautions toprevent inhaling the dust.

As will be apparent to one of skill in the art, this method is highlyeffective at providing a single layer of powder on a carrier, but is notsuitable for over-coating a carrier or for applying one or more “coats”of different agricultural input powder to a carrier.

That is, the carrier will be coated with more than a single layer of theagricultural input. In some embodiments, the carrier may be coated witha single agricultural input powder between 0.1% (w/w) to 5% (w/w) asdiscussed above or the agricultural carrier may be coated with two ormore agricultural input powders, wherein each powder forms a separatelayer or coating around the carrier.

Accordingly, in another aspect of the invention, there is provided afertilizer product comprising a dry agronomic carrier coated with a finedry powder of at least one agricultural input, wherein the agriculturalinput powder has been ground such that at least half of the particlesare of an average diameter between 10 and 90 microns, said powder beingpresent on the carrier at 0.1%-5.0% (w/w) of the carrier.

In an attempt to increase application rates, the inventors tested addingminute amounts of liquid in an effort to encourage powder to powderbinding and thereby increasing coating of the agronomic carrier. Asdiscussed in U.S. Pat. No. 7,445,657, the addition of liquids such asbinders can damage some carriers, causing either a breakdown in theintegrity of the carrier or in the case of seeds, reducing emergenceefficiency. Furthermore, the addition of the liquid only increasedbinding by approximately 50% over the single layer surface area coatingattained with direct dry to dry application.

Subsequently however, as discussed herein, it has been discovered thatapplying an electrostatic charge of between 15 kV to 100 kV, preferably,in some embodiments, 75 kV to 100 kV, under an air pressure of 8 to 20psi promotes greater adhesion of the powder to the carrier, as discussedbelow.

As a result of carrying out the process under air pressure, the powderflows in a directable jet, which improves coating of the carrier, asdiscussed herein. Specifically, the pressure helps to better distributethe agricultural input powder during the coating process.

Furthermore, the combination of the generated electrostatic charge andthe air pressure promotes increased adhesion to the carrier,specifically, the air pressure directs the powder towards the carrierbut also disperses the particles so that individual particles of thepowder are charged, thereby improving adhesion of the powder.

As will be readily apparent to one of skill in the art, as a result,much higher coatings, for example, 4-5% can be attained using thismethod.

Furthermore, in some embodiments, the combination of the electrostaticcharge and the air pressure reduces dust, as discussed below.

As will be appreciated by one of skill in the art, by virtue of thecoating rates now attainable, multiple layers of powder may be appliedso that different agricultural inputs may be applied to a singlecarrier, for example, a pesticide and a fertilizer or a fungicide and aninoculant. Other suitable combinations will be readily apparent to oneof skill in the art and are within the scope of the invention.

Referring to FIG. 1, the method of the invention is shown schematicallyin one possible embodiment or arrangement. Therein, the agriculturalinput, indicated as a nutrient powder, is released from a feeder into acharging chamber which includes electrodes powered by an electricalgenerator. As discussed above, the agricultural input powder iselectrostatically charged within the charging chamber. The chargedagricultural input powder is then released from the charging chambersuch that the charged powder comes into contact with the agronomiccarrier, indicated in FIG. 1 as being granular fertilizer products,thereby coating the agronomic carrier. As will be apparent to one ofskill in the art, other suitable arrangements for applying a chargedagricultural input powder to an agronomic carrier are also within thescope of the invention and this arrangement is intended for illustrativepurposes only.

In preferred embodiments, there is provided a method forelectrostatically adhering fine, dry nutrient particles in powder formto agronomic carriers such as granular fertilizers or planting seed,which comprises the steps of:

-   -   Feeding nutrient particles (powder) into a charging chamber or        through a charging point along the blending pathway.    -   In the charging chamber introducing (a) a charge such that a        metal component (stinger, paddle, auger or other surface) is        grounded, and (b) the desired powder through an electrostatic        charging system (such as a triboelectric gun or corona discharge        apparatus) wherein the powder will preferentially take two        steps (i) it will drive towards the grounded surface and        then (ii) it will then move onto the granular carrier as the        carrier particles pass by or contact the metal surface that is        coated with the powder.    -   This results in an amount of powder adhesion that is much higher        than can be achieved with mechanical agitation. Furthermore,        there is a reduction in the amount of dust because of the        preferential movement of the powder particles to the charged        surface

One embodiment of the system for carrying out the method or process ofthe invention is shown schematically in FIG. 1.

As will be appreciated by one of skill in the art, other suitablearrangements are within the scope of the invention and this embodimentis provided for illustrative purposes.

Therein, an agricultural input powder 10 is released from feeder 12 intocharging chamber 20. The charging chamber 20 includes grounded metalcomponent 22 which is connected to an electrical generator 24. Asdiscussed above, while the agricultural input powder 10 is within thecharging chamber, the particles of the powder are charged. The chargedagricultural input powder 10A particles are then released from thecharging chamber 20. In some embodiments, the release of the chargedagricultural input powder 10A particles is regulated and/or facilitatedby a spreader 30 at a base of the charging chamber 20 which promotesseparation of the particles. Specifically, the charged agriculturalinput powder 10A particles are released from the charging chamber 20onto a belt conveying agronomic carriers 32 to be coated. As discussedabove, the charged agricultural input powder 10A particles adhere to andcoat the agronomic carriers 32.

The invention will now be explained by way of examples; however, theinvention is not necessarily limited by the examples.

A metallic container was used in a lab scale experiment to mimic a fullscale fertilizer blending container. A metallic beater was used torepresent a moving blender part (such as a paddle, baffle, stinger orauger).

The container and metallic beater were grounded (negatively charged).Then the metallic container was filled with 500 to 1000 gram samples ofurea. The granules were put into motion.

Powdered (a) iron and (b) boron were delivered into the container via acharging gun (corona). The gun was charged at rates ranging from 75 to100 kV and air pressure was delivered at 8 to 20 psi. Total amountadhering onto the urea or sulphur was weighed. The powder was 100 to 325mesh in the trial.

The whole process was repeated, this time using only mechanical mixingto attain coatings of the powders onto the urea or sulphur.

Results

1) Iron Powder Coating on to Urea Prills

% coated Treatment Descriptor (w/w) Dust evaluation Standard coating Addpowdered 0.63 Moderate dust (direct application nutrient blend and inwork area without electrical mix mechanically charge) Electrocharge Addnutrient powder 1.5 Little dust in gun/air pressure to urea through workarea (charge applied to electrically charged particles, blender “gun”with air surface grounded, pressure urea positively charged by inductionfrom the ground)

Note that (a) the total amount adhering to the urea particles was morethan doubled when a charged system under light air pressures wereintroduced, and (b) there was a noticeable reduction in dust in the workarea

2) Boron Powder Coating on to Urea Prills

% coated Treatment Descriptor (w/w) Dust evaluation Standard coating Addpowdered 0.82 Moderate dust (direct application nutrient blend and inwork area without electrical mix mechanically charge) Electrocharge Addnutrient powder 1.48 Little dust in gun/air pressure to urea throughwork area (charge applied to electrically charged particles, blender“gun” with air surface grounded, pressure urea positively charged byinduction from the ground)

Note that (a) the total amount adhering to the urea particles was morethan doubled when a charged system under light air pressures wereintroduced, and (b) there was a noticeable reduction in dust in the workarea.

While the preferred embodiments of the invention have been describedabove, it will be recognized and understood that various modificationsmay be made therein, and the appended claims are intended to cover allsuch modifications which may fall within the spirit and scope of theinvention.

What is claimed is:
 1. A method for adhering an agricultural inputpowder to an agronomic carrier comprising: electrostatically charging aquantity of dry agricultural input powder in a charging chambercomprising a grounded metal component and bringing the agronomiccarriers in contact with the ground such that the carrier becomesgrounded such that the electrostatically charged powder moves towardsthe grounded agronomic carrier metal component; and passing theagronomic carriers by the charged powder such that the charged powderadheres to the carrier.
 2. The method according to claim 1 wherein theelectrostatic charge is applied to the agronomic input powder at from 15to 100 kV
 3. The method according to claim 1 wherein the chargingchamber is at an air pressure between 0-4 BAR.
 4. The method accordingto claim 1 wherein the agronomic carrier is selected from the groupconsisting of: seeds; nitrogen fertilizer products; phosphate fertilizerproducts; potassium fertilizer products; sulfur fertilizer products;calcium fertilizer products; magnesium fertilizer products; urea prills;dry fertilizer products; granular fertilizer products; inert pellets;and biodegradable pellets.
 5. The method according to claim 1 whereinthe agricultural input powder is selected from the group consisting of:a fungicide; an insecticide; a nutrient; a fertilizer powder orcomponent thereof; an inoculant; a soil amendment; a micronutrients; andcombinations thereof.
 6. The method according to claim 1 wherein atleast 50% of the powder passes through a 100 MESH screen.
 7. The methodaccording to claim 1 wherein the powder is between 100 MESH to 450 MESH.8. The method according to claim 1 wherein the powder is between 100MESH to 325 MESH.
 9. The method according to claim 1 wherein at least50% of the powder is in the form of particles having a diameter betweenabout 10 and about 90 microns.
 10. The method according to claim 5wherein the agricultural input is a nutrient and the nutrient isselected from the group consisting of: nitrogen, phosphorus, potassium,calcium and magnesium.
 11. The method according to claim 5 wherein theagricultural input is a micronutrient and the micronutrient is selectedfrom the group consisting of zinc, copper, manganese, boron, iron,magnesium, molybdenum, chloride, selenium, phosphate, nitrogen,potassium, and sulfur.
 12. The method according to claim 1 where theelectrostatic charge is applied at a rate between 25 kV to 100 kV. 13.The method according to claim 1 where the electrostatic charge isapplied at a rate between from 15 kV to 25 kV.
 14. The method accordingto claim 1 where the electrostatic charge is applied at a rate betweenfrom 15 kV to 50 kV.
 15. The method according to claim 1 where theelectrostatic charge is applied at a rate between from 15 kV to 75 kV.16. The method according to claim 1 where the electrostatic charge isapplied at a rate between from 25 kV to 75 kV.
 17. The method accordingto claim 1 where the electrostatic charge is applied at a rate betweenfrom 25 to 50 kV.
 18. A fertilizer product comprising a dry agronomiccarrier coated with a fine dry powder of at least one agriculturalinput, wherein the agricultural input powder has been ground such thatat least half of the particles are of an average diameter between 10 and90 microns, said powder being present on the carrier at 0.1%-5.0% (w/w)of the carrier.
 19. The fertilizer product to claim 18 wherein theagronomic carrier is selected from the group consisting of: seeds;nitrogen fertilizer products; phosphate fertilizer products; potassiumfertilizer products; sulfur fertilizer products; calcium fertilizerproducts; magnesium fertilizer products; urea prills; dry fertilizerproducts; granular fertilizer products; inert pellets; and biodegradablepellets.
 20. The fertilizer product to claim 18 wherein the agriculturalinput powder is selected from the group consisting of: a fungicide; aninsecticide; a nutrient; a fertilizer powder or component thereof; aninoculant; a soil amendment; micronutrients; and combinations thereof.